In recent years, with the continuing investigation and research in the field of nanotechnology, materials with one-dimensional nanostructures, such as silicon nanowire (SiNW), have attracted more and more attention. SiNW has advantages of significant quantum effect and large surface to volume ratio, which brings a bright prospect for applications in the fields of MOS devices, sensors, and so on.
As an elementary cell of the biochip, SiNW devices have been widely used for bio-detection and diagnostics. Referring to FIG. 1a and FIG. 1b, the conventional method of producing SiNW devices includes covering an oxide layer 2022 on the surface 2021 of the polycrystalline/monocrystalline silicon to form the SiNW 202 as well as the SiNW device area B on both sides of the SiNW 202. The principle of the SiNW devices produced in such way is similar to the principle of the MOSFET. The oxide layer on the polycrystalline/monocrystalline silicon is utilized as gate oxide, by which the bio-molecule groups with electric charges are absorbed. These charges can adjust the potential of the SiNW in a similar way to adjust the potential of the MOSFET, and then the conductivity properties of SiNW can be affected. Therefore, the specified bio-molecule groups can be identified by monitoring the conductivity properties of the SiNW.
FIG. 2 is a schemic diagram of the basic structure of a conventional SiNW device in prior art. The extremely narrow polysilicon wires covered with oxide films of evenly thickness are exposed to the external environment, and the SiNW device area B is covered with an insulating layer. In the conventional semiconductor technology, photolithography and etching technology are usually applied to achieve the above basic structure. However, due to the anisotropic etching properties, the mini spacers 211 may be formed on the SiNW outside the device area B. Furthermore, plasma etching may result in the damage of the SiNW.